1. Field of the Invention
The present invention relates to a gamma correction, and more particularly, to a gamma correction device capable of controlling a gamma voltage easily and accurately, a gamma correction method thereof, and a liquid crystal display device using the same.
2. Discussion of the Related Art
With rapid advancement towards an information-oriented society, demands for flat panel displays having excellent characteristics such as slim profile, lightweight, and low power consumption have been on the increase. Examples of flat panel display devices includes plasma display panels (PDPs), organic light-emitting devices (OLEDs), and liquid crystal display devices (LCDs). Because LCDs have excellent resolution, color-display characteristics, and image quality, LCDs are actively used in notebook computers, monitors for desktop computers, televisions, and the like.
In general, LCDs have a liquid crystal material formed between two substrates with respective electrodes. The orientation of the liquid crystals is changed due to an electric field generated according to a voltage applied to the two electrodes. Thus, an image can be displayed by controlling transmittance of light according to the changed liquid crystal orientation.
FIG. 1 is a schematic view of a related art LCD. As illustrated in FIG. 1, the related art LCD includes a plurality of gate lines GL0 to GLn, a plurality of data lines DL1 to DLm, a liquid crystal panel 2, a gate driver 4, a data driver 6, a gamma voltage generator 8, and a timing controller 10. The liquid crystal panel 2 includes thin film transistors TFTs and pixel electrodes formed at intersections of the gate lines and the data lines, and displays a predetermined image. The gate driver 4 supplies a scan signal to the gate lines GL1 to GLn of the liquid crystal panel 2. The data driver 6 supplies a predetermined data signal to the data lines DL1 to DLm of the liquid crystal panel 2. The gamma voltage generator 8 supplies a plurality of gamma voltages to the data driver 6. The timing controller 10 generates control signals for controlling the gate driver 4 and the data driver 6.
The liquid crystal panel 2 is formed with liquid crystal material injected between a first glass substrate and a second glass substrate. The plurality of gate lines GL0 to GLn and the plurality of data lines DL0 to DLm are formed on the first glass substrate intersecting each other. The TFTs are formed at the intersections of the gate lines and the data lines to drive the pixel electrodes.
The timing controller 10 supplies red (R), green (G), and blue (B) data signals from the display system (not shown) to the data driver 6. Additionally, the timing controller 10 generates a gate control signal and a data control signal for controlling the gate driver 4 and the data driver 6 using a horizontal sync signal (Hsync) and a vertical sync signal (Vsync) supplied from the display system. The gate control signal is applied to the gate driver 4, and the data control signal is applied to the data driver 6.
The gate driver 4 generates scan pulses sequentially in response to a gate control signal supplied from the timing controller 10, and supplies the scan pulses sequentially to the gate lines GL1 to GLn of the liquid crystal panel 2. The data driver 6 receives R, G, B data and a predetermined control signal from the timing controller 10. The data driver 6 supplies an analog data signal to the data lines DL1 to DLm of the liquid crystal panel 2 in response to the data control signal supplied from the timing controller 10.
More specifically, the data driver 6 receives digital data signals related to an image and outputs analog data signals to drive the pixel electrodes to display the image. To achieve such a result, the gamma voltage generator 8 generates a gamma voltage, which is a reference voltage needed to generate the analog data signal from the data driver 6. Accordingly, the data driver 6 generates an analog data signal using a gamma voltage generated from the gamma voltage generator 8 in response to the digital data signal.
The gamma voltage generator 8 is generally prepared separately from the data driver 6. That is, the gamma voltage generator 8 and the timing controller 10 are generally seated together on a data printed circuit board (PCB). As illustrated in FIG. 2, each of the gamma voltages GMA1 to GMA6 generated from the gamma voltage generator 8 is obtained from terminal points between a plurality of series resistances. The plurality of series resistances are disposed between a power voltage Vdd and ground. That is, the gamma voltages GMA1 to GMA6 are generated through a voltage distribution between the resistances by connecting a plurality of resistances R1 to R6 in series.
Each of the gamma voltages GMA1 to GMA6 is supplied to the data driver 6 and is used as a reference voltage for generating the analog data signal. That is, each of the gamma voltages GMA1 to GMA6 is supplied to a resistance-string part (not shown) of the data driver 6 and is derived into a preferred gray scale level (e.g. 256 gray-scale levels) by the resistance-string part. Accordingly, the data driver 6 outputs the analog data signal by selecting a gray-scale level corresponding to the digital data signal.
The gamma voltages GMA1 to GMA6 generated from the related art gamma voltage generator 8 can be controlled by users of the LCD. In particular, when the gamma voltage is adjusted for a product test, it is difficult for the user to adjust the gamma correction. Therefore, a simple technique is needed to adjust the gamma correction easily and accurately.
Additionally, the gamma voltage can be controlled by the related art gamma voltage generator 8 using an analog gamma correction. Accordingly, it is very difficult to achieve an accurate gray curve using the analog gamma correction.